Pressure grouting

ABSTRACT

A method for grouting the annulus between the jacket and piling in the legs of an offshore structure in which air is introduced to expel water from the lower end of the annulus, and the annulus is then filled from the top with grouting material. Water may be pumped down the annulus to wash out mud. Some grout may be pushed out the bottom of the annulus to remove mud or to form a bell foundation.

United States Patent Bassett 1 Sept. 3, 1974 [54] PRESSURE GROUTING 3,60l,999 8/1971 Olsen cl al (ll/46 [75] lnventor: Max Bassett, Houston, Tex. [73] Assignee: C. Nelson Shields, Jr., Trustee. Primary Examiner-Jacob Shapiro Houston, TeX. Attorney, Agent, or Firm-Murray Robinson; Ned L. [22] Fi'ed: Aug 14, 1973 Conley; David Alan Rose [2]] Appl. No.: 388,085

Related U.S. Application Data 7 T C [63] Continuation-impart of Set. No. 358,009, May 7, [5 1 ABS RA T I973, abandoned.

A method for grouting the annulus between the jacket [52] U.S. Cl 61/46, 6l/53.52, 6l/53.6, and piling in the legs of an offshore structure in which 6l/53.74 air is introduced to expel water from the lower end of [51] Int. Cl E02d 5/74, E02d 5/42, E02b 17/00 the annulus, and the annulus is then filled from the top [58] Field of Search 61/46, 46.5, 53.52, 53.6, with grouting material. Water may be pumped down 61/56, 56.5, 50, 52, 53.74 the annulus to wash out mud. Some grout may be pushed out the bottom of the annulus to remove mud [56] References Cited or to form a bell foundation.

UNITED STATES PATENTS 8/1971 Rochelle 61/46 10 Claims, 8 Drawing Figures PATENTEUSEPB m4 3 3% sum 1 or 3 PAIENIEusm ISM sum 20F a PATENTEU 3EP3 I974 SHEEP 3 OF 3 PRESSURE GROUTING CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of my copending application Ser. No. 358,009, filed May 7, 1973, and entitled Improvements in Pressure Grouting, and now abandoned. The invention of this application is an improvement over the subject matter of copending application Ser. No. 378,196, filed July 11, 1973, for a reissue of U.S. Pat. No. Re. 3,601,999. In addition, the subject matter of this application is related to the subject matter of my copending application Ser. No. 351,261, filed Apr. 16, 1973. All of the foregoing applications are assigned to the assignee of the present application, and are exclusively licensed to The Western Company of North America, as is the present application. Application Ser. No. 380,730, filed July 19, 1973 by Arthur Frank Tragesser, Jr., assigned to The Western Company of North America, also discloses related subject matter.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the grouting of offshore structures.

2. Description of the Prior Art Offshore structures have come into increasing use in recent years to support platforms for drilling of oil and gas wells and for producing oil and gas from such oil wells. Such structures may be erected in water from comparatively shallow depths up to several hundred feet deep. A variety of forms of structure and methods of construction of such platforms have been utilized. One such method which has been found to be particularly desirable in deep water is that which is illustrated, for example, in U.S. Pat. No. 3,209,544 to Borrmann, in which the legs of the structure are fabricated and assembled on shore. The legs are hollow, and may be sealed to make the structure buoyant, so that it can be towed out to the desired offshore location. Valves in the legs are opened to allow flooding with sea water, so that the leg structure will sink in a vertical position and settle onto the bottom. As the legs sink they fill with water up to the water level of the sea. It will be appreciated that the legs will sink into the ocean bottom a distance dependent upon the weight of the structure and the softness of the ocean bed.

A platform which is built only on such legs would have a high degree of instability, particularly in heavy storms. It has, therefore, been the practice to more rigidly connect the structure to the ground by driving hollow steel pilings down through the legs, which then become jackets for the pilings. When a piling is dropped down through a jacket, it knocks off the seals closing the bottom ends of the jackets, so that the jackets tend to sink deeper into the bottom, and mud and silt from the bottom may enter the annulus between the piling and the jacket.

When the piling has been fully driven (usuallyto refusal), it has been the practice to fill the annulus between the piling and the jacket with a grouting material which solidifies in place. This not only increases the rigidity and, therefore, the strength of the structure, but also helps to keep out water so as to prevent corrosion of the piling. If the grouting fills the annulus all the way down to the bottom of the jacket, the piling is protected through the soft mud of the sea bed.

Various methods have been utilized for grouting such structures. One method, as shown in the aforesaid Borrmann patent, for example, requires the use of a seal member at the bottom of the annulus. In this method the grouting material is pumped into the bottom of the annulus and rises upwardly therein to the top. This method usually requires the use of divers, and in addition, it often fails to produce fully satisfactory results because water cannot be effectively excluded from the annular space so that the grouting material becomes diluted and difficult to set.

Evans et al., in U.S. Pat. No. 3,492,824, describe a method comprising injecting air into the top of the annulus to expel water through a nipple at the bottom of the annulus, and then injecting grouting material through the bottom nipple. The grouting material is supposed to rise up through the annulus to above the water line, displacing air out the top. As a practical matter such a system would be very unsatisfactory. The ocean bed is normally soft and porous at the bottom of the jacket so that as soon as enough grouting material is pumped in to overcome the hydraulic head of the overlying sea water, the grouting material would begin to run out the bottom of the jacket and would be lost. Thus, it would be necessary to utilize some kind of seal or closure at the bottom of the annulus to hold the grouting in.

Evans et al. also disclose a method whereby air is injected into the nipple at the bottom of the annulus to drive the water upwardly through the annulus out the top. It is apparent that such a system would be extremely inefficient in expelling water, since the air, being lighter, will rise up through the water. The same problem of losing grout out the bottom would also exist in this method.

Blount et al., in their US. Pat. No. 3,5 64,856 disclose another grouting system in which the grouting material is injected through nipples at the bottom of the annulus. He uses water to wash out mud from the location of his injection nipples upwardly, but he makes no attempt to remove water or mud from below the injection point. Furthermore, his annulus is filled with water at the start, which must be expelled upwardly by the rising grouting material. Thus a large excess of grouting material would be necessary in order to insure that all of the water is expelled out of the top of the annulus.

Olsen and Bassett disclose, in their U.S. Pat. No. 3,601,999, a system which avoids many of the problems encountered in other grouting systems. The present invention is an improvement over that system.

SUMMARY OF THE INVENTION According to the present invention, water is expelled from the annular space out its lower end by the application of air pressure, fluid grouting material is introduced into the annular space and flows to the lower end thereof while sufficient air pressure is maintained on the annular space to prevent water from returning, and the grouting material is allowed to set up in the annular space. In one embodiment of the invention water is circulated through the annular space either before or after the air injection in order to wash mud out. In another embodiment of the invention, sufficient air pressure is applied to the grouting material, before it sets up, to force a portion of it out the lower end of the annular space to form a bell around the lower end of the jacket. In still another embodiment of the invention, a relatively small amount of grouting material, insufficient to counteract the hydraulic head of the overlying sea, is injected into the annulus, and air pressure is applied to it until it sets up, thereby forming a plug in the bottom of the annulus.

Other features of the invention may be best explained in connection with the accompanying drawing and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view showing a typical installation of an offshore structure on the sea bed;

FIG. 2 is a semi-schematic view of apparatus suitable for practicing one embodiment of the method of this invention;

FIG. 3 is an enlarged fragmentary vertical sectional view of one of the legs of the structure of FIG. 1, showing the method step of expelling water from the annulus between the jacket and the piling of the legs;

FIG. 4 is a fragmentary sectional view, similar to the lower portion of FIG. 3, and showing a portion of the grouting material in place according to one embodiment of the invention;

FIG. 5 is a fragmentary vertical sectional view of one of the legs of the structure showing the grouting material in place;

FIG. 6 is a vertical sectional view of the application of this invention to another form of offshore structure;

FIG. 7 is a vertical sectional view of the application of this invention to still another form of offshore structure; and

FIG. 8 is a horizontal sectional view of the structure of FIG. 7, taken at line 8-8 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 of the drawing, a typical offshore structure 10 is shown, such as is used in the oil and gas industry for offshore drilling and production. The structure 10 as shown is only the base portion which is being installed on the sea bed 12, prior to providing the base portion with the usual platform and superstructure (not shown). The structure 10 includes a plurality of supporting legs, each in the form of a tubular jacket 13 which extends downwardly from above the water line 14 into the sea bed 12, the several leg jackets being secured together by cross members 15 and diagonals 16 in a conventional manner. As is known, the sea bed is usually comparatively soft and porous, and in many instances the structure 10 (not including pilings) will sink of its own weight until the jackets 13 sink as much as 30 feet into the sea bed.

When the structure 10 is properly placed the pilings 17 are driven through the jackets into the sea bed, usually to the point of refusal, to provide a final support for the platform. As shown, the pilings are normally of tubular steel, and are usually of at least one pipe size smaller than the size of the jackets, so that an annular space 18 exists between each piling and its surrounding jacket. The annular space is not, of course, unifonn, since no means are used to center the piling in the jacket. On the average, however, the annulus will have a radial thickness of from I inch to 2% inches depending upon the size of the installation. It is this annulus which must be filled with grouting material, particularly in the region of the lower end of the jacket 13, not only in order to attain leg rigidity sufficient to withstand tides, storms, ocean currents and the like, but also to protect the piling and the inside of the jacket against corrosion by sea water and air.

After the piling 17 has been driven through the jacket 13 into the sea bed 12, the piling is cut off at the upper endof the jacket and the two components are secured together as by welding in a heavy steel ring 19, prior to installation of the deck and other superstructure. The welding in this ring 19 provides a pressure tight seal at the top of the annulus 18.

One form of apparatus which has been found suitable for performing the method of this invention is shown in somewhat schematic form in FIG. 2. In this structure two pressure tanks 30, 32 are provided for storage tanks for dry cement. These pressure tanks may, for example, be of the type provided with an air slide bottom, as shown in US. Pat. No. 2,609,125 to Schemm or as shown in US. Pat. No. 2,934,223 to Scruby et al. In such structure dry cement is put into the tanks and lies on a porous sloped bottom, and air flowing through the bottom fluidizes the material in the tank to cause it to flow down the slope. In the structure shown air for such fluidizing is provided by a low pressure air compressor 34, from which air passes through conduit 36, 38 to tanks 30, 32 respectively. Valves 40, 42 are provided to control flow to one or the other of the tanks.

Fluidized cement is carried from the pressure tanks through conduits 44, 46, through which flow is controlled by valves 48, 50. The fluidized cement flows from one of the tanks at a time to a surge tank 52 provided with a suitable dry material valve 54 at its lower end. The valve may, for example, be of the type shown in US. Pat. No. 2,858,966 to Pfening. When the valve 54 is opened the dry cement falls into a hopper 56 which is connected at its lower end to a mixing chamber 58. A nozzle 60 extends into the mixing chamber, perpendicular to the outlet of the hopper 56 and coaxially with a mixed cement line 62. Water is provided to the nozzle 60 by means of a suitable pump 64 which takes suction from a water storage tank 66 through a water line 68. The water tank may be provided with any convenient gauge so that the amount of water used can be accurately determined.

It will be appreciated that cement falling from the hopper 56 into the mixing chamber 58 is thoroughly admixed into water sprayed from the nozzle 60. The mixture passes through the line 62 into a slurry tub '70. A suitable pump 72 takes suction from the slurry tub through a line 74 and pumps the fluid grouting material into the annulus between the jacket 13 and the piling 17 through a pipe or hose 76, which is provided with a check valve 86 to allow flow only toward the annulus. Centrifugal pumps are satisfactory in many instances, but where high pressure is required, as in deep water installations, a reciprocating pump may be more desirable.

To provide high pressure air for expelling water from the annulus and for the grouting operation, a high pres sure air compressor 78 is provided. This air compressor provides air through a conduit 80, fitted with a suitable valve 82, a pressure gauge 84, and a bleed line 83 having a valve 85 therein. The pressure gauge is preferably one which reads in feet of sea water, for a purpose which will hereinafter be explained. To avoid getting grout in the air line, the line 76 may be connected below, and on the same side of the jacket as, conduit 80, as shown in FIGS. 3, 4 and 5.

In the practice of a preferred embodiment of the method of this invention, air under pressure is introduced into the annulus 18 by operating the compressor 78 and adjusting the valve 82 to allow flow through the line 80 to the annulus, bleed valve 85 being closed. As air pressure is increased in the annulus, it will force the water therein downwardly and out the bottom. In some instances, however, the jacket 13 may be resting within a highly compacted bottom formation so that the air pressure available is insufficient to force water through it. In such an event water under high pressure may be pumped into the annulus by means of the pump 72 until the formation is broken down enough to allow water to be forced through it by air pressure. The pump is then shut off and air pressure utilized to expel the water from the annulus.

As may be seen in FIG. 3, a crack or other opening 90 in the jacket, or an open jacket flooding valve (not shown) may be readily detected by the method of this invention. As the level of water drops in the annulus, the air pressure required to expel the water continuously increases at a rate proportional to the level of water in the annulus. Thus, with a pressure gauge reading in feet of salt water, the depth to which the water level in the annulus has been lowered at any given time can be read directly on the pressure gauge. An observer of the pressure gauge will note a continuing steady increase in the pressure reading. When the water level in the annulus reaches an opening 90 in the jacket, the pressure in the annulus will stop increasing, or at least the rate of increase will be substantially diminished, because air will be lost from the annulus through the opening 90, as illustrated by the bubbles 92. A diver may then be sent down to close the opening, and the expulsion of water by means of air pressure may be resumed.

As has previously been noted, mud, comprising sea water and such solid materials as may form the sea bed, will in many cases fill the annulus from the bottom of the jacket to approximately the level of the bottom of the sea bed 12. It is particularly important that substantially all of such mud be removed from the annulus, so that there will be no voids in the grouting material which is to be placed therein. Such voids, filled with mud and sea water, not only greatly reduce the strength and rigidity of the structure, but also provide means by which corrosion of the piling and of the interior of the jacket is greatly accelerated. The method of this invention, wherein water in the annulus is expelled out the bottom of the annulus, allows the washing out of mud in the annulus by means of the downwardly moving water.

When all of the water has been expelled from the annulus this will be apparent from the surface because air escaping from the bottom of the annulus may be detected as air bubbles rising to the surface. At this time the compressor may be stopped, valve 82 closed, and the valve 85 opened to bleed air pressure from the annulus until the bubbles stop rising to the surface. The pressure gauge 84 should then read a pressure equal to the pressure head of the sea water. This pressure is held on the annulus to insure that water and mud do not come back up into the annulus at the bottom.

In some instances it may be desirable to further wash out mud at the lower end of the annulus. This may be accomplished by circulating additional water through the annulus, using the pump 72 to pump water. Since this water falls a substantial distance in the annulus, it will have a tendency to erode any mud remaining in the annulus. If desired, air pressure in the annulus can be increased at this time to insure that the circulating water is blown out the bottom of the annulus.

When the operator is satisfied that the annulus has been properly cleaned of mud, circulation of the water is stopped and air pressure is again brought back to a level just enough to keep water and mud out of the lower end of the annulus, i.e. equal to the sea water head. The structure is now ready for grouting.

The preferred grouting material to use is an expanding type grouting material, i.e. one which expands during at least a portion of the setting period. Such a material has'a greater bond to steel in shear than ordinary grouting materials. This has been found to be an important consideration in achieving a maximum strength structure. Expanding type cements have been known for use in the construction industry, where they are known as self-compensated cements. Various additives such as sodium chloride may be added to cement to make it expand. One expanding type cement useful to form expanding type grouting materials is that sold under the trademark CHEMP-COMP, manufactured by Texas Industries, Inc.

To make the grouting material, water is mixed with the cement in the ratio recommended by the cement manufacturer or in accordance with the standards of the American Petroleum Institute. Such water ratios make a fluid grouting material which may have a viscosity from 5 to 20 poises. A grouting material within this range is viscous enough that it will have little tendency to flow through the mud in which the jacket 13 is positioned. Such grouting materials usually have a density of from about 14 to 16 pounds per gallon (i.e. about twice the density of water) although grouting materials having densities outside this range may also be used in the practice of the method of this invention.

Ina typical grouting operation, an initial batch of grouting material sufficient to till 8 to 10 linear feet of the annulus is pumped in at a rate of, for example, 2 to 3 barrels per minute. In the usual operation when this initial batch of grouting material has had time to fall to the bottom of the annulus, air pressure is released enough to compensate for the pressure head exerted by the grouting material, so that the pressure at the bottom of the annulus is maintained at that pressure required to prevent water and mud from rising in the annulus.

Pumping of grout into the annulus is then resumed, either continuously or in batches, while the air pressure is bled off through the bleed valve at a rate such as to maintain the pressure at the bottom of the annulus equal to or slightly greater than the pressure head of the overlying sea water. This may be determined by continuous checking of the amount of water being pumped in from the water tank 66 and comparing the height of grout which this would cause in the annulus with the reading of the pressure gauge 84. This operation is continued until a hydrostatic balance between the grouting material and the head of sea water is reached. At this point no air pressure is required to prevent water from moving upwardly'into the annulus. In a typical situation the annulus should then be approximately one-half full of grout, since the density of the grout is approximately twice that of sea water.

When the air pressure in the annulus has been reduced to atmospheric, the compressor 78 and its associated conduit valve and pressure gauge may be moved to another leg of the platform to begin expelling water from that leg.

In a preferred embodiment of the invention it is then desirable to pump in enough additional grouting material to get at least about 8 to feet of additional height of grouting material in the annulus. The pressure created by this additional grouting material will force the grouting material out the bottom of the annulus and carry out any water that may have seeped upwardly and any mud that may remain at the bottom of the annulus. This grouting material which is forced out will flow into any voids in the'mud'created by the water which was previously expelled from the annulus, and in many cases the pressure of the grouting material will force the surrounding mud away from the lower end of the jacket. if desired, additional grouting material can be introduced in the annulus at this time to increase the amount which is expelled from the bottom of the annulus. This expelled material when it sets up will form a foundation bell which will greatly increase the stability of the structure.

Such expulsion of grouting material from the bottom of the annulus may be achieved at an earlier stage of the grouting operation by maintaining a pressure at the bottom in excess of the pressure needed to balance the head of the sea.

When. an adequate amount of grouting material has been introduced to remove mud and water from the bottom of the annulus, and to form a foundation bell, if one is utilized, a small amount of quick-setting grouting material is pumped into the annulus. It is usually necessary to have only enough of the quick-setting grouting material to fill the annulus a distance of from 1 to 3 feet, because this has been found to be sufficient, when set up, to support the weight of the fluid grouting material which is to be put on top of it, filling the annulus up to above the water line.

Quick-setting cements are well known in the art, usually being formed by adding a material such as calcium chloride. Because only a small amount of quick-setting grouting material is used, it is possible to sacrifice strength for timesaving achieved by relatively rapid setting. For example, any of the various quick-setting cements described in the aforesaid patent to Blount et al. may be used satisfactorily. It will be appreciated that this short portion of quick-setting grouting material will set up quite rapidly as compared to the grouting material below it in the annulus. As soon as the setting of this small portion is completed, the regular grouting material may again be pumped into the annulus to fill it up to the top. This grouting material is allowed to set up and the grouting job is then completed.

The method of this invention has thus far been described in terms of this application to a structure like that illustrated in FIGS. 1 to 5 of the drawing, in which both the piling and the jacket extend to above the water line. However, the method is equally applicable to other types of offshore structures in which either the piling or the jacket, or both, terminates below the water line. Examples of such structure are illustrated in the aforesaid patent to Borrmann. Thus, as illustrated in FIG. 6 herein, a jacket 113 may have a funnel top 111 and a resilient annular seal member 119, made of synthetic rubber or the like, within the upper end of the jacket. The jacket extends down into the sea bed 12, but terminates well below the surface 14 of the water. A piling 117 is driven down through the seal 119 and into the sea bed. The water is blown out of the annular space 118 between the piling and the jacket by means of air supplied through a conduit 180. Grout is then injected into the annular space through a grouting line 176, and the grouting process proceeds as previously described herein. The air and grouting lines may, if desired, be removed by divers or by means of automatically detachable couplings, such as explosive couplings.

Still another form of offshore structure is illustrated in FIGS. 7 and 8. In this form of structure a bell bottomed jacket member 213 is enlarged at its lower end 211 to provide a space for a plurality of pilings 217. In the application of the method of this invention to this structure the space surrounding the pilings in the enlarged portion 211 of the jacket is sealed off, as by welding in a plate 219 just above the ends of the pilings. However, the plate could be welded in at any other point at a higher elevation in the jacket. The upper ends of the pilings 217 may also be closed by welding in plates or otherwise, but in many cases this will not be necessary because the pilings will be driven deep into the ground. Thus air can be supplied through a line 280 to force water out the lower end of the enlarged portion 211 of the jacket, grout can then be supplied through a line 276, and the grouting process then carried out as hereinbefore described.

Although the grouting operation of this invention has been described in terms of grouting the legs of a new offshore structure, it is apparent that the procedure is also suitable for grouting old completed structures which were not grouted upon initial construction. The method of this invention can also be used in grouting structures in which a seal is provided at the bottom of the annulus, if the seal is one which will allow flow outwardly from the annulus. In some prior art grouting procedures an inflatable packer is used to close the bottom end of the annulus. Such packers can be deflated as necessary to allow expulsion of water or grouting material from the lower end of the annulus.

In a variation of the invention, after all of the water has been expelled from the annulus, a short plug, up to 8 to 10 feet in length, of quick-setting grouting material is pumped in and held at the bottom of the annulus by air pressure until it sets up. The air pressure can then be released and the remainder of the annulus filled with the usual grouting material, preferably the expanding type material. This method of operation helps to insure an absence of air pockets or water pockets throughout the major portion of the annulus. The quick-setting plug has closed the bottom so water cannot enter, and the filling of the remainder of the annulus in the absence of air under pressure reduces the possibility of pressurized air bubbles being trapped.

Ordinarily it is preferred to use a cement-base grouting material for its strength and relatively low cost. However, in some installations other materials are preferred for various reasons. For example, a sand slurry may be used, or epoxy or various plastic materials may be used, where a higher modulus of elasticity in the grouting material is desired. The invention is equally applicable to the use of such materials, and the terms grouting material" or grout" as used herein are intended to include all materials which are suitable for the practice of the steps of the invention.

Although several embodiments of the invention have been shown and described herein, the invention is not limited to such embodiments but instead extends to the full scope of the accompanying claims.

I claim: y

l. A method of grouting an offshore structure having at least one supporting leg including a substantially vertically extending tubular jacket in the water and a piling in said jacket having an outside diameter smaller than the inside diameter of the jacket whereby a space is formed between the inside of the jacket and said piling; said space being closed at its upper end and open to the sea bed at its lower end, wherein said space initially has mud in at least the lower portion thereof, said method comprising the steps of flowing water down through said space and out the lower end to wash out the mud,

expelling the water from the space out its lower end by application of air pressure,

flowing fluid grouting material down through said space to the lower end while maintaining sufficient air pressure to prevent water from returning, and permitting the grouting material to set.

2. A method as defined by claim 1 and including causing a portion of said grouting material to flow out the lower end of the space to form a bell around the lower end of the jacket.

3. A method as defined by claim 1 wherein an initial portion of the grouting material is allowed to flow to the bottom of the space, and air pressure is applied to it until it sets, and then flowing additional grouting material into the space,

and

allowing the additional grouting material to set.

4. A method as defined in claim 1 and including injecting water into said space prior to the insertion of any grouting material, and causing the injected water to flow out the lower end of the space.

5. A method of grouting an offshore structure having at least one supporting leg including a substantially vertically extending tubular jacket in the water and a piling in said jacket having an outside diameter smaller than the inside diameter of the jacket whereby a space is formed between the inside of the jacket and said piling, said space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of pumping water into said space at a pressure sufficient to force water out the lower end of the space through the sea bed formation, then applying sufficient air pressure to said space to force substantially all of the liquid out the lower end, flowing fluid grouting material down through said space to the lower end while maintaining sufficient air pressure to prevent water from returning, and

permitting the grouting material to set up. 6. A method as defined by claim 5 and including causing a portion of said grouting material to flow out the lower end of the space before it sets up, so that upon setting the grouting material will form a bell around the lower end of the jacket. 7. A method as defined by claim 5 wherein an initial portion of the grouting material is allowed to flow to the bottom of the space, and then flowing additional grouting material into the space. 8. A method as defined by claim 7 wherein said initial portion of grouting material is insufficient to compensate for the pressure head of the overlying sea, and wherein air pressure is maintained on the grouting material sufficient to compensate for said pressure head until said initial portion of grouting material sets up.

9. A method of grouting an offshore structure having at least one supporting leg including a tubular jacket extending downwardly from above the waterline to the sea bed and a piling driven through said jacket into the sea bed with an annular space existing between the inside of the jacket and said piling, said annular space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of applying air under pressure to said annular space to force water therein out the lower end, while maintaining sufficient air pressure to keep out the water, flowing grouting material to the lower end of said annular space and allowing it to set up,

releasing the air pressure,

flowing additional grouting material into the annular space, and

allowing the additional grouting material to set up.

10. A method of grouting an offshore structure having at least one supporting leg including a tubular jacket extending downwardly from above the waterline to the sea bed and a piling driven through said jacket into the sea bed with an annular space existing between the inside of the jacket and said piling, said annular space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of applying air under pressure to said annular space to force water therein out the lower end, thereby reaching an air pressure in said annular space sufficient to overcome the pressure head of the overlying sea water,

flowing fluid grouting material down through said annular space to the lower end, while gradually reducing air pressure to compensate for the pressure head exertedby the grouting material, until sufficient grouting material is in the annular space to overcome the pressure head of the overlying sea water without the use of any air pressure,

flowing an additional amount of fluid grouting material into said annular space, whereby fluid grouting material is forced out the bottom of the annular space, and

allowing the grouting material to set up.

Disclaimer 3,832,857.-Maw Bassett, Houston, Tex. PRESSURE GROUTING. Patent dated Sept. 3, 1974. Disclaimer filed Mar. 11, 1976, by the assignee, 0. Nelson Shields, J12, trustee. Hereby enters this disclaimer to claim 9 of said patent.

[Ofiicial Gazette May 4, 1.976.] 

1. A method of grouting an offshore structure having at least one supporting leg including a substantially vertically extending tubular jacket in the water and a piling in said jacket having an outside diameter smaller than the inside diameter of the jacket whereby a space is formed between the inside of the jacket and said piling; said space being closed at its upper end and open to the sea bed at its lower end, wherein said space initially has mud in at least the lower portion thereof, said method comprising the steps of flowing water down through said space and out the lower end to wash out the mud, expelling the water from the space out its lower end by application of air pressure, flowing fluid grouting material down through said space to the lower end while maintaining sufficient air pressure to prevent water from returning, and permitting the grouting material to set.
 2. A method as defined by claim 1 and including causing a portion of said grouting material to flow out the lower end of the space to form a bell around the lower end of the jacket.
 3. A method as defined by claim 1 wherein an initial portion of the grouting material is allowed to flow to the bottom of the space, and air pressure is applied to it until it sets, and then flowing additional grouting material into the space, and allowing the additional grouting material to set.
 4. A method as defined in claim 1 and including injecting water into said space prior to the insertion of any grouting material, and causing the injected water to flow out the lower end of the space.
 5. A method of grouting an offshore structure having at least one supporting leg including a substantially vertically extending tubular jacket in the water and a piling in said jacket having an outside diameter smaller than the inside diameter of the jacket whereby a space is formed between the inside of the jacket and said piling, said space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of pumping water into said space at a pressure sufficient to force water out the lower end of the space through the sea bed formation, then applying sufficient air pressure to said space to force substantially all of the liquid out the lower end, flowing fluid grouting material down through said space to the lower end while maintaining sufficient air pressure to prevent water from returning, and permitting the grouting material to set up.
 6. A method as defined by claim 5 and including causing a portion of said grouting material to flow out the lower end of the space before it sets up, so that upon setting the grouting material will form a bell around the lower end of the jacket.
 7. A method as defined by claim 5 wherein an initial pOrtion of the grouting material is allowed to flow to the bottom of the space, and then flowing additional grouting material into the space.
 8. A method as defined by claim 7 wherein said initial portion of grouting material is insufficient to compensate for the pressure head of the overlying sea, and wherein air pressure is maintained on the grouting material sufficient to compensate for said pressure head until said initial portion of grouting material sets up.
 9. A method of grouting an offshore structure having at least one supporting leg including a tubular jacket extending downwardly from above the waterline to the sea bed and a piling driven through said jacket into the sea bed with an annular space existing between the inside of the jacket and said piling, said annular space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of applying air under pressure to said annular space to force water therein out the lower end, while maintaining sufficient air pressure to keep out the water, flowing grouting material to the lower end of said annular space and allowing it to set up, releasing the air pressure, flowing additional grouting material into the annular space, and allowing the additional grouting material to set up.
 10. A method of grouting an offshore structure having at least one supporting leg including a tubular jacket extending downwardly from above the waterline to the sea bed and a piling driven through said jacket into the sea bed with an annular space existing between the inside of the jacket and said piling, said annular space being closed at its upper end and open to the sea bed at its lower end, said method comprising the steps of applying air under pressure to said annular space to force water therein out the lower end, thereby reaching an air pressure in said annular space sufficient to overcome the pressure head of the overlying sea water, flowing fluid grouting material down through said annular space to the lower end, while gradually reducing air pressure to compensate for the pressure head exerted by the grouting material, until sufficient grouting material is in the annular space to overcome the pressure head of the overlying sea water without the use of any air pressure, flowing an additional amount of fluid grouting material into said annular space, whereby fluid grouting material is forced out the bottom of the annular space, and allowing the grouting material to set up. 